1. Field of the Invention
The invention relates to a thermally-assisted magnetic recording head in which near-field light is applied to a magnetic recording medium to lower a coercivity thereof so as to record information, and to a head gimbal assembly, a head arm assembly, and a magnetic recording unit that each include the thermally-assisted magnetic recording head.
2. Description of Related Art
In the past, a magnetic recording unit such as a Hard Disk Drive (HDD) has been used for recording and reproducing magnetic information (hereinafter, simply referred to as “information”).
The magnetic recording unit typically includes, in the housing thereof, a magnetic recording medium (a magnetic disk) in which information is recorded, and a magnetic read write head that performs write operation and read operation of the information. The magnetic read write head is formed on a surface of a magnetic head slider, and has an air-bearing surface facing the magnetic disk. The magnetic head slider is attached to an end of a suspension, and the other end of the suspension is attached to a pivotable arm.
In recent years, along with a progress in higher recording density (higher capacity) of the magnetic disk, improvement in performance of the magnetic read write head has been demanded. Therefore, as a magnetic recording system capable of addressing higher recording density, a so-called thermally-assisted magnetic recording system has been studied. In the thermally-assisted magnetic recording system, a magnetic disk in which coercivity of a magnetic recording layer is large is used, and a magnetic field for recording (recording magnetic field) and heat are applied to a recording region (a region in which information is recorded) of the magnetic recording layer at the time of information recording. Therefore, coercivity of the recording region is lowered with increase in temperature as well as the recording region is magnetized, and thus information is recorded.
In the thermally-assisted magnetic recording system, near-field light is generally used for supplying heat to a magnetic disk. Along with this, a magnetic recording head of the thermally-assisted magnetic recording system (a thermally-assisted magnetic recording head) includes a light source generating laser light, a waveguide allowing the laser light to propagate therethrough, a magnetic pole generating a recording magnetic field, a plasmon generator provided in a region between the waveguide and the magnetic pole, and a cladding layer allowing the plasmon generator to be embedded in the region between the waveguide and the magnetic pole. In the thermally-assisted magnetic recording head, when surface plasmons are generated by the plasmon generator, near-field light is generated in the vicinity of the air-bearing surface by using the surface plasmons, and therefore heat is supplied together with the recording magnetic field to the magnetic disk.
In the case where such near-field light is used, in Japanese Patent No. 4104584, surface plasmon polariton coupling is used to prevent overheating of a plasmon generator due to direct application of light. In this case, the light propagating through a waveguide (guided light) is not directly applied to the plasmon generator, and the guided light is coupled with the plasmon generator through evanescent coupling, and thus surface plasmon polaritons are generated on a surface of the plasmon generator.
In the case where such surface plasmon polaritons are used, in U.S. Pat. No. 8,089,831, to concentrate the guided light effectively, a width of a plasmon generator is decreased in the vicinity of an air-bearing surface. Specifically, the plasmon generator includes a forward section having a uniform width and a backward section having a width larger than the uniform width, in order backward from the air-bearing surface.
During operation of the thermally-assisted magnetic recording head, since temperature is drastically increased in the vicinity of the air-bearing surface where the near-field light is generated, thermal expansion occur. As a result, large stress is applied to the plasmon generator, and thus the plasmon generator is easily agglomerated (shrunk). In this case, in particular, the forward section close to the air-bearing surface is likely to be increased in temperature as compared with the backward section, and the forward section having a volume relatively smaller than that of the backward section is easily exposed to high pressure environment, and therefore the forward section is more easily agglomerated.
If the forward section is agglomerated, the plasmon generator gets away from the magnetic disk at the time of recording, and therefore the near-field light is less likely to be generated in the vicinity of the air bearing surface. As a result, since it is difficult to control the coercivity of the magnetic disk, recording performance is deteriorated.
To prevent deterioration of the recording performance caused by the agglomeration, in Japanese Unexamined Patent Application Publication No. 2011-008899, an adhesive layer is provided between a plasmon generator and a dielectric body. In a forward section having a small volume, however, a surface area (an area contacted to the adhesive layer) thereof is also small, and thus it is difficult to suppress agglomeration of the forward section only by providing the adhesive layer.
Accordingly, it is desirable to provide a technique capable of suppressing agglomeration of a plasmon generator in order to obtain superior recording performance.